The present invention generally relates to valve mountings for hydraulic systems in power machines. In particular, the present invention relates to the direct mounting of valve actuators on valve blocks.
Machines such as skid steer loaders and other power machines employing conventional hydraulic systems need valves for their operation. These valves utilize linear actuation mechanisms. Currently, linear actuators are not directly mounted on the valve surface, but instead, they are mounted on a separate portion of the system such as a support plate. The sliding plunger of the actuator is connected to the spool of the valve. Since the linear actuator is positioned separate from the valve, the sliding plunger and the portion of the valve spool extending from the valve block have to be covered by a sealed rubber boot in order to prevent penetration by any dust from the exterior.
The separation of the actuator and the valve poses several problems in conventional systems. Some of the problems include:
1. The rubber boot provides limited protection from dirt, but over a period of time dirt penetrates into the area surrounding the plunger and the exterior of the spool.
2. The plunger may not be aligned with the spool, thereby resulting in reduced efficiency as a result of all the force not acting in a linear direction.
3. The valve and the actuator have separate tolerances due to being spaced apart.
4. The center line of the plunger is offset from the center line of the spool resulting in a possibility of an induced moment.
5. Mounting of the actuator on the support plate prevents rotation of the motor about the axis of the plunger and thereby does not provide for good clearance of other parts.
The valve assembly of the present invention utilizes a linear actuator that is mounted directly on the valve block around an exterior projection of the valve spool. The direct mounting of the actuator on the valve block provides a substantially air tight mounting for the valve assembly.
Direct mounting of the actuator on the valve block can be efficiently utilized in machines such as skid steer loaders and other power machines that employ hydraulic circuits for their operation.
An illustrative embodiment of the valve assembly has an actuator which has a sleeve with an internal plunger that can be moved within the sleeve. One end of the sleeve has an actuator motor that drives the plunger and the other end of the sleeve has a flange. The sleeve also has a collar with a pair of bores through which screws can be passed to bolt the sleeve rigidly to the valve mount. A retainer seal with a cylindrical groove and a pair of bolt holes provides an interface between the actuator sleeve and the valve block. The retainer seal also has a grooved portion called the O-ring groove which is dimensioned to receive the flange on the sleeve such that an air tight coupling is made between the sleeve and the retainer seal.
Therefore, one embodiment of the invention provides a direct and rigid coupling between the linear actuator and the valve block.
An embodiment of the invention also provides a direct coupling between the linear actuator and the valve surface which is sufficiently tight so that dirt is prevented from penetrating into the valve bore.
An embodiment of the invention further provides and maintains a linear connection between the plunger and the spool at all times.
A further aspect of the invention prevents the pin connection between the plunger and the spool from slipping by always maintaining the pin within a cylindrical portion.
These embodiments and aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims and accompanying drawings.